Siren



Sept. 20,1938. 0. 1. H. :EKMAN' S IREN Filed July 2, 1954 3 Sheets-Sheet 1 Sept. 20, 1938. o. I. H. EKMAN v SIREN Filed July 2, 1934 3 Sheets-Sheet 2 v v 50 f I Sept. 20, 1938.

SIREN Filed July 2, 1934 3 Sheets-Sheet 3 Patented Sept. 20, 1938 l UNITED STATES PATENT orrtce Olof Ingelnar Harald Ekman, Stockholm, Sweden Application July 2, 1934, Serial No. 733,497 In Sweden March 21, 1934 7 Claims. (01. 11e 147) This invention relates to sound producingde- In the accompanying drawings several embodivices particularly sirens, of the type comprising ments of the invention are illustrated in a ,sub- 9. blade wheel or rotor and a surrounding casstantially diagrammatic manner. Fig. 1 is a side ing or stator formed with sound openings, through elevation, partly in section, of a siren comprising which air is driven out at intervals by the rotata rotor and a stator. Fig. 2 is a top plan view ing blade Wheel so as to produce the sound in of Fig. 1. Fig. 3 is a horizontal section of the the well-known way. The invention relates more siren, the section being taken with the object in specifically to sirens of this type which are adapt- View of showing the blade wheel. Fig. 4 is an ed to throw the sound in a definite direction or axial section of a siren having a rotary com- 1' directions 'orin varying directions. An object pressor and a. receiver for the compressed air. 1 of the invention is to provide a siren of this Fig. 5 is a horizontal section on the line VV kind whichis efficient in operation and simple of Fig. 4. Fig. 6 is a diagrammatic section of in construction. V l the blade wheel of the apparatus shown in Fig. "One featiireof the invention'involves the pro- 4- Fig- 7 s an a a ect o Of an app 16 Vision of means, by which only one blade or a like that of Fig. 4, but provided with a conduit fewblades of the rotor is or are allowed to for restoring air to the inlet of the compressor operate at a time so that substantially the enfrom the parts of the blade wheel not in optire effectot the driving motor will be utilized in eration. Fig. 8 is a cross section on the line expelling air from this blade or blades. To this VIII-VIII of Fig. '7. Fig. 9 is an axial section end the casing is provided with a wall or partiof a modified embodiment having a radial flow 20 tion covering the inlet to the blade wheel and compressor and a receiver for the compressed havinga'n opening thereinwhich cooperates with air. Fig. 10 is a. cross section of this apparatus. the blades of the wheel for controlling the flow Fig. 11 is a detail view. Fig. 12 is an axial secof the airthrough the'device, for instance, by tion of a modified form of the apparatus shown admitting'ainto a certain part of the blade in Fig. 7, and Figs. 13 and 14 are cross sections 25 wheel onlyat any given time. on the lines XEIL-XIII and XIV-911V, respecln'orcler that in a siren of this type the entively of 12 the effect of the. driving motor may be utilized With reference to Figs. 1-3, the numeral I by one blade or by only a few blades. at a time, indicates the driving motor, the shaft 2 of which the blades of the rotor must be made larger carries the blade wheel. The blade wheel com- 30 than the blades of a siren built for the same prises a circular disk 3'attached to the shaft effect, but in which admission of air takes place 2 w ch carries a number o blades 4. As shown to the'entire blade wheel at the same time, and in ge 'b ade 4 are Shaped as hollow in which the sound is simultaneously thrown in sectors, closed at all sides, which form peripherall directions, or the speed o-f the rotor must y Op Sector-Shaped Sp s e wee the be increased at unchanged size of the blade wheel. The blade wheel is surrounded with a very lit- This is trueespecially in case of sirens, in which l cl r n by a w 5 carried y the frame the'emis'sion of the sound takes place through a of the motor I which is formed wi a plurality single sound opening or through asingle amplifyof openings 9 corresponding in size and num- 40 ing horn. Asthe driving motor, as a rule, run ber to the spaces of the blade Wheel. Above the 40 at its maximum speed, it will be necessary in blade wheel, the wall 5 carries an end wall 1 order-to satisfy the above said conditionto incoverin the inlet of the blade Whe1 With the crease the radial or axial length of the blade ex p n of a ll in1et op n Said p nwheel or both these lengths. Such an increase, g y, a y, as 'shown in Fig. e Shaped however, must be very great, if the emission of as a sector corresponding to the space between 45 the soundtakes place through a single h each two blades of the blade wheel. It is to from one sound opening in the casing or from be noted that the shape and number of blades only a few 'soundopenings. Another object of n op n s y be varied r r ilythe invention is, therefore, to provide means for In e rotat o Of he b ade Whee ai enters obtaining an increased efficiency of the blade through the opening 8, as soon as a space of 50 wheel, without increasing its dimensions or speed, the blade Wheel comes into register with said or with a very small increase of these factors. To opening. This air will then be expelled at a high this end I provide in front of the wall or parspeed through the nearest opening 5, thereby protition covering the inlet of the blade wheel a ducing sound in well-known way. The remain- 55, receiver for the compressed air. ing openings 6 arenot in operation and can be left out of consideration. It is to be noted that the sound openings 6 may be provided with horns to amplify and direct the sound, or a separate casing having such horns may be mounted around the wall 5. In case of a single sound opening, which may or may not have a. horn, the wall together with the cover I may be made rotatable in order to permit variation of the direction of the sound.

In the embodiment shown in Figs. 4-6, the driving shaft 2 in addition to the blade wheel It) carries a compressor wheel ll. Said compressor wheel is positioned at a certain distance from the blade wheel leaving a chamber l2 between it and the blade wheel. The blade wheel, the chamber l2 and the compressor wheel are all surrounded by a casing 14. The part of said casing surrounding the blade wheel is provided with a horn l5 leading from two sound openings I6, I! in the casing. In the casing, between the chamber l2 and the blade wheel, is a partition I3 formed with a sector-shaped opening I8 adjacent the opening IS in the circumferential wall of the casing, said opening l8 also extending somewhat beyond the edge of the opening l6, remote from the horn, as shown in Fig. 5. The casing l4 may either be stationary or rotatably adjustable about the shaft 2 to permit adjustment of the horn to the desired direction.

In operation, the compressor wheel H receives air through inlet openings in the casing and forces the air down into the chamber I2 which receives the air from all of the blades of the compressor wheel and acts as a storage chamber for the compressed air. As the pressure exerted by the compressed air upon the casing l4 ives rise to considerable friction due to the tendency of the air to rotate with the wheel H, it is of importance to reduce said friction. To this end, the chamber I2 is surrounded by a wall I9 rigidly connected to the periphery of wheel I I so as to rotate therewith. Between said wall !9 and the casing l4 there is a suitable packing 20 to prevent leakage of air. The compressed air stored up in the chamber l2 passes through the opening ill in the partition l3 down to the blade wheel 10 which may be assumed to rotate in the direction of the arrow in Fig. 5. In this rotation, the blade wheel receives air in one of its blade spaces, before said space comes into communication with the sound opening and, as a result, a certain preliminary compression of this air will be effected, before the space reaches the sound opening l6 and allows the air to emerge therethrough. After the said space has passed the sound opening [6 and the blade following said space moves below opening IS in the partition I3, the said space will still carry a certain amount of compressed air with it. This air is allowed to escape through the second sound opening II. In order to promote the emission of the air through the opening I! into the horn I5, the latter may be provided with a baffle 21 between the openings l6 and I1. said baiile being so shaped and arranged as to cause the air expelled through the opening I 6 to produce a suction in the passage leading from the opening II.

The air contained in the storage chamber I2 acts as a buifer during the operation, balancing the pressure shocks produced by the compressor wheel II and producing a substantially constant pressure above the outlet opening l8. Due to the fact that the blade wheel Ill is supplied with air already compressed, the blade wheel need not be made of such size as would otherwise be necessary for a given final pressure on the air, as it emerges into the horn. In other words, the effect of the driving motor will be distributed to the two wheels I!) and II so that each of them performs a stage of the compression work.

In Fig. 6 is shown a blade wheel having sectorshaped blades like those shown in Fig. 3, with the exception that the blades are solid instead of hollow. It is well known to make the blades of sirens in the shape of very thin radial walls each provided with an arc-shaped circumferential projection extending rearward with relation to the direction of rotation. In such a wheel is thus formed a pocket between each blade and its pro- J'ection, and in said pocket air will be retained and eddy currents will be produced, thereby reducing the efficiency of the wheel. In the blade wheels shown having sector-shaped spaces to receive the air, no such eddy current production and no retaining of air can take place. In such a wheel the rear wall of the blade forms a guide wall for the compressed air, allowing it to emerge at high speed, as soon as said wall has passed beyond the rear edge of the sound opening it. It is to be noted that, of course, said rear wall need not be radial, as shown in the drawings, but may be arc-shaped in some suitable way.

Instead of a single horn, as shown in the drawings, several horns may be used, each leading from one or more sound openings in cooperation with an inlet opening l8 for each horn. If it is desired to have several horns cooperate, it is necessary to take care that the emission through them takes place absolutely at the same time. In the spacing of the respective inlet openings IB care must be taken that the distances the air must pass on its way from the various openings l8 to the outlet ends of the respective horns will be exactly the same, so that the emission of the sound from the various horns will take place exactly at the same time.

It is of importance to provide the best sealing possible between the blade wheel, the casing and the partition during the compression period. To this end, the clearances between the blade wheel on the one hand and the casing and partition on the other hand may be reduced in the neighbourhood of the opening l8 and the horn I 5 to the smallest value possible, as indicated in Fig. 5.

Due to the admission of air to a part of the blade wheel only at any given time it will be possible to avoid the heavy friction losses which in directed emission through one or a few outlets, would otherwise arise due to the fact that the blades when passing along those portions of the casing, where there are no sound openings, will carry compressed air with them, which will produce a great friction as a result of its pressure upon the casing. It is to be noted, however, that it is impossible to prevent a certain amount of air of a pressure above atmospheric from being carried by the blades during the passage of the blades below the unapertured portion of the partition 43. In order to overcome said drawback, a connection may be provided leading from the corresponding portion of the casing to the inlet side of the compressor wheel II, as shown in Figs. 7 and 8. In these figures the portion of the casing not occupied by the horn I5 is surrounded by a jacket 30 connected by ports 3| to the interior of the casing outside the blade Wheel which leads to the space above the compressor wheel II. The outlet end of the jacket may be shaped as an ejector, causing the compressor to exert a suction on the-air contained in the jacket 39, thereby promotingthe evacuation of the parts of the blade wheel out of operation for the time being. This evacuation may, of course, be performed in a different way, without departing from the principle of the invention.

In the form shown in Fig. 9 the driving shaft 2 carries a compressor wheel 40 of radial flow type which delivers its compressed air to an annular channel 4| of successively increasing section of passage bounded outwards and inwards by walls 42 and 43, respectively, carried by thecompressor wheel. As shown, the wall 42 is connected to the wheel 40 by partitions 40' which form the operating blades of the wheel, while wall 43 is directly connected to the wheel 40. The compressor wheel and the wall 42 are enclosed in a casing 44 havin a partition 45 below the passage 4|. Said partition 45 is formed with an opening 46 at its outer portion. Said opening is of a limited peripheral length and of a radial length corresponding approximately to half the radius of the partition 45. Below the partition 45 is a blade wheel 41 provided with an annular air guiding surface 48 curved in conformity with the curvature of the wall 43. i The casing 44 is formed with a sound opening 49 from which leads a horn 50. In this case the channel 4| acts as a storage chamber for the compressed air produced by the compressor wheel 46.

a higher compression can be obtained than bythe use of an axial flow compressor of the same dimensions, as in the first mentioned compressor the centrifugal force contributes to the compression. The air when escaping from the compressor wheel 49 into the diffuser channel 4| has a tendency to continue its rotation, particularly in the uppermost portion of the channel and, as a result, the air entering the passage 4| beyond that edge of theopening 46 where the blades leave the opening on their rotation, must rotate almost through the entire circle before it reaches the opening 46 and is delivered to the blade wheel. In order to suppress this tendency, I provide inside the channel 4| at a certain distance from the said edge of the opening 46 a radial baflle 5| upstanding in the channel from the partition 45, said baffle, as shown in Figs. 10 and 11, being curved so as to divide the air, deflecting the air striking the concave surface thereof back again towards the opening 46, while allowing the air on the convex surface of the baflle to continue its rotation with the walls 42, 43.

In Fig. 12 is shown an apparatus like the one shown in Fig.7 but provided with means to evacuate the horn alternately with the emission of air therethrough. To this end, the horn I5 is formed with an enlarged chamber 52 at its inner end. Said chamber 52 opens both towards the blade wheel 53 and towards a rotary valve 54 situated below the blade wheel and carried by the driving shaft 2 thereof.

The blade wheel comprises alternately sectorshaped blades and sector-shaped spaces open at the periphery of the blade wheel. Said spaces are also open both at the top and bottom of the blade wheel. The valve 54 comprises a disk attached to the shaft 2 which is provided with an upstanding peripheral flange 55, having an aperture right below each space of the blade wheel. Above the blade wheel 53 is a partition 56 in the casing 51 and below the blade wheel is another partition 58. The partition 56 is formed with an opening 59 of limited angular extent to admit compressed air from the storage chamber 60 to the blade wheel (see also Fig. 13), whereas the partition 58 presents an unapertured portion right below the opening 59 but is formed with'an opening 6| in front of said unapertured portion, as seen in the direction of rotation or the blade wheel (see also Fig. 14). The shaft 2 carries a compressor wheel 62 above the chamber 69. The casing 51 is provided with ajacket 63 surrounding the casing save the portion thereof occupied by the chamber 52. Said jacket communicates with the interior of the casing by openings 64 situated outside the blade wheel.

In operation, when a space of the blade wheel is incomi'nunication with the chamber 66 through the opening 59 and receives compressed air, said air will be forced out at high speed by the blade wheel into the chamber 52 of the horn to produce sound. At the same time communication between the chamber 52 and the interior of the valve 54 is. interrupted by an unapertured portion of the flange 55. When the chamber 52 is out of communication with any space of the blade wheel, an aperture of the flange 55 brings about communication between the chamber 52 and the interior of the valve 54. By way of the opening (Si in the portion 58 and the inoperative spaces of the blade wheel the chamber 52 is in communication with the jacket 53 and is, consequently, subjected to a suction. By this means the chamber 52 will alternately be subjected to pressure and to vacuum with resulting amplifying of the sound generation.

What I claim is:-

l. A siren having a rotatable shaft, a blade wheel on said shaft and having an air outlet at its periphery, a casing surrounding said blade Wheel formed with a sound opening in its peripheral wall, a horn carried by said casing and projecting radially therefrom and communicating with said sound opening, and a wall in said casing covering an inlet face of the blade wheel, said wall having an eccentrically positioned opening for admission of air to only part of the crosssectional area of the blade wheel, said casing and said wall being rigidly connected to each other and mounted for rotary adjustment about said shaft so that the direction in which the horn extends may be changed by rotary adjustment of the casing and the air admission opening is simultaneously correspondingly adjusted.

2. In combination, a siren having a rotatable shaft, a blade wheel on said shaft and having an air outlet at its periphery, a surrounding casing formed with sound emission openings, a valve to control the admission of air to the blade wheel, a compressor wheel on said shaft, and a storage chamber for compressed air situated between said compressor wheel and valve for receiving compressed air from the compressor wheel and supplying the compressed air to the blade wheel under the control of the valve.

3. In combination, a siren having a rotatable shaft, a blade wheel on said shaft and having an air outlet at its periphery, a surrounding casing formed with sound emission openings, a valve to control the admission of air to the blade wheel, a compressor wheel on said shaft, a storage chamher for compressed air situated between said compressor wheel and valve for receiving compressed air from the compressor wheel and supplying the compressed air to the blade wheel under the control of the valve, and a circumferential wall connected to said compressor wheel and surrounding said storage chamber.

4. In combination, a siren having a shaft, a blade wheel on said shaft and having an air outlet at its periphery, a surrounding casing formed with a sound emission opening, a horn leading from said opening for directing the sound, a wall covering the inlet of the blade wheel and having an opening for admission of air to a part only of the blade wheel at any given time, said last mentioned opening being situated immediately in advance of the sound opening and having a greater peripheral length than said sound openmg.

5. A siren having a shaft, a blade wheel carried by said shaft and having an air outlet at its periphery, a casing surrounding said blade wheel and having a sound emission opening, a partition in said casing covering the inlet of the blade wheel and having an opening immediately in advance of said sound opening, the casing having an additional sound opening out of the range of the opening in the partition, and a horn leading from said two sound openings.

6. A siren having a shaft, a blade wheel carried by said shaft and having an air outlet at P its periphery, a casing surrounding said blade wheel and, having a sound emission, opening, a partition in said casing covering the inlet of the blade wheel and having an opening immediately in advance of said sound emission opening, the casing having an additional sound opening out of the range of the opening in the partition, and a horn leading from said two sound openings, said horn being formed with a separate passage for each of said sound openings, one of said passages being arranged to act as an. ejector with respect to the flow of air through the other passage.

'7. A sirenhaving a shaft, a blade wheel on said shaft and having an air outlet at its periphery, a compressor wheel on said shaft, an air storage chamber between said compressor wheel and said blade wheel, a casing surrounding said blade wheel, said compressor wheel and said chamber, a partition in said casing-in front of the inlet end of the blade wheel, said partition having an opening'for admission of air'to part of the cross sectional area of the blade wheel, said casing having a sound emission opening formed therein and a horn leading from said sound emission opening.

OLOF INGEMAR HARALD EKMAN. 

